The NADPH oxidase inhibitor diphenyleneiodonium is also a potent inhibitor of cholinesterases and the internal Ca2+pump
The NADPH oxidase inhibitor diphenyleneiodonium is also a potent inhibitor of cholinesterases and the internal Ca2+pump
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DOI：
10.1111/j.1476-5381.2009.00394.x
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发表时间：
2009-10-01
影响因子：
7.3
通讯作者：
Janssen, L. J.
中科院分区：
文献类型：
--
作者：
Tazzeo, T.;Worek, F.;Janssen, L. J.
背景和目的：二苯基碘鎓（DPI）常被用作NADPH氧化酶抑制剂，但越来越多地发现其具有不相关的副作用。实验方法：采用离体牛气管平滑肌条，观察其等长收缩作用。胆碱酯酶活性测定使用分光光度法;内部钙泵活性进行了评估，由钙离子摄取到平滑肌microsomes.Key结果：收缩乙酰胆碱显着增强DPI（10-4 M），而那些卡巴胆碱（CCh）没有，这表明可能抑制胆碱酯酶。DPI显著抑制由CCh、KCl和5-HT引起的收缩，并且在其他持续反应中也揭示了阶段性活动。直接生物化学测定证实，DPI是乙酰胆碱酯酶和丁酰胆碱酯酶的有效抑制剂（IC 50分别类似于8 × 10-6 M和6 × 10-7 M），具有可逆的混合非竞争性抑制作用。DPI对CCh收缩的抑制作用不被另一种NADPH氧化酶抑制剂（夹竹桃苷）模仿，也不被Src抑制剂PP 1或PP 2模仿，排除了通过NADPH氧化酶信号通路的作用。激动剂诱发反应的DPI介导的抑制的几个特征（即峰值幅度的抑制和阶段性活动的暴露）类似于环匹阿尼酸（内部Ca 2+泵的抑制剂）的那些特征。直接测量微粒体Ca 2+摄取显示，DPI适度抑制内部Ca 2 + pump.Conclusions和影响：DPI抑制胆碱酯酶活性和气管平滑肌的内部Ca 2+泵。
Background and purpose:Diphenyleneiodonium (DPI) is often used as an NADPH oxidase inhibitor, but is increasingly being found to have unrelated side effects. We investigated its effects on smooth muscle contractions and the related mechanisms.Experimental approach:We studied isometric contractions in smooth muscle strips from bovine trachea. Cholinesterase activity was measured using a spectrophotometric assay; internal Ca2+ pump activity was assessed by Ca2+ uptake into smooth muscle microsomes.Key results:Contractions to acetylcholine were markedly enhanced by DPI (10-4 M), whereas those to carbachol (CCh) were not, suggesting a possible inhibition of cholinesterase. DPI markedly suppressed contractions evoked by CCh, KCl and 5-HT, and also unmasked phasic activity in otherwise sustained responses. Direct biochemical assays confirmed that DPI was a potent inhibitor of acetylcholinesterase and butyrylcholinesterase (IC50 similar to 8 x 10-6 M and 6 x 10-7 M, respectively), following a readily reversible, mixed non-competitive type of inhibition. The inhibitory effects of DPI on CCh contractions were not mimicked by another NADPH oxidase inhibitor (apocynin), nor the Src inhibitors PP1 or PP2, ruling out an action through the NADPH oxidase signalling pathway. Several features of the DPI-mediated suppression of agonist-evoked responses (i.e. suppression of peak magnitudes and unmasking of phasic activity) are similar to those of cyclopiazonic acid, an inhibitor of the internal Ca2+ pump. Direct measurement of microsomal Ca2+ uptake revealed that DPI modestly inhibits the internal Ca2+ pump.Conclusions and implications:DPI inhibits cholinesterase activity and the internal Ca2+ pump in tracheal smooth muscle.